The present invention relates to the cure rate of SiH-olefin platinum catalyzed addition-cured compositions. More particularly, the present invention relates to a method for controlling the cure rate of SiH-olefin platinum catalyzed silicone foam compositions.
Silicone foam compositions are known in the art. Reference may be made, for example, to U.S. Pat. Nos. 4,189,545; 3,923,705; 4,599,367, and 3,436,366.
Silicone foam is generally prepared from foamable compositions containing a vinyl-containing siloxane, a hydride containing siloxane, a hydroxyl source, and a platinum catalyst. These compositions undergo cure to form foam. The term "cure time" refers to the time required for a foamable composition to become foam. Various applications of silicone foam compositions sometimes require increasing or decreasing cure times without sacrificing density or strength of the foam. Presently, cure speed is adjusted by varying the concentration of the vinyl polymer and the silane functionality in the foamable composition. This approach is impractical, however, because it requires adjusting the entire formulation depending on the end use of the foam.
Alternatively, cure speed can be adjusted by adjusting the level of catalyst used. This approach works well for achieving rapid cure but when the catalyst concentration is lowered to effect a cure time of 8 minutes, trace amounts of added amine, phosphine, or other base additives completely poison the platinum catalyst such that cure is not observed.
It is therefore an object of the present invention to provide a method for accurately controlling cure time of a silicone foam composition which does not require the adjustment of the entire formulation of the foam.
It is further an object of the present invention to provide a method for accurately controlling cure time which can tolerate the presence of an acidic or basic impurity.
These objects are achieved in the present invention.